Electric conversion.



S. GABOT. E

ELECTRIC CONVERSION. APPLICATION FILED AUG. 22, 1912.

L 12 43 v Patented 0013.6,1914.

PATENT EW'ALZL CABGT, 9F BROUZLLENE, MASSACHUSETTS.

CUNVEESION.

Specification of Letters .atent.

Patented @c't. ti, lfii i.

A l lication filed Au ust 22, 1812. Serial No. Fl 6.360.

To all whom it may concern:

Be it known that I, SEWALL Caner, citizen of the United States, andresident of Brookline, in the county of Norfolk and State ofMassachusetts, have invented a new and useful improvement in ElectricConversion, of which the following is a specification.

My invention relates to the conversion of lternating current to directcurrent by synchronous commutation.

The object of my invention is to provide a system for. oommutatingalternating current supplied on a substantially constantpotentia basisso as to obtain a practically steady directcurrent on a substantiallycon-- stant-current basis when the counter E. M. F. of the workingcircuit is not greater than about 50% of the A. C. source.

A further object of my invention is to minimize the sparking on thecommutator, such sparking having a tendency to occur when the counter E.M. F. of the working circuit changes and to persist until he angle ofcommutation is shiited.

In the drawings which accompany an form a part of this specification, .ihave illus trated one form of apparatus and an arrangement of circuitswhereby the foregoing objects may be realized.

in the drawings: Figure l is a diagram showing the commutator in suchposition that current will. flow from the source to the working circuit;and ifig. 2 is similar diagram showing the commutator in position toshort-circuit the connections of the source to the working circuit.

In the figures, S represents a preferably current.

L is an inductance, the function of which source of is togovern thevalue of current in the working or direct-current circuits.

9", and T are two connnutating segments suitably secured to and rotatingwith the shaft 15 of a l-pole synclnl'onous motor energized by thesource S or else secured to and rotating with the shaft of a st-pole A.C. generator. Brushes o, 1),, are suitably secured to the f 'ame A whichis adjustable about the shaft l) and thus constitutes the equivalent ofa rocker arm. These brushes make electrical contact with the connnutatorsegments and their function to reverse synchronously the connections ofthe A. C. source to the D. C. working circuit and also to short-circuitsaid connections tor-the requisite interval of time to obtain sparklesscommutation.

L is an inductance in the D. C. or working circuit and its function isto reduce the fluctuations in the value of the current in the Workingcircuit, and also to minimize changes in th angular position of thebrushes required for sparkless commutation.

In designing the foregoing system, i prefer to make the value of L inhenries approximately equal to the maximum E. In. F. of the sourcedivided by twelve times the product or" the amperes in the Workingcircuit by frequency of the source in cycles per second. I also preferto make the dura t-ion of the short-circuit equal approximately to theduration of a quarter of a cycle of the alternating current developed bysaid source and to make the value of L in henries large as compared withthe value of l have found that if the inductance L is made adjustable.sparkless commutation may be obtained. through wide ranges of load, andhence of counter M. F, in the working 'circuit without any shifting ofthe angle of commutation.

The operation is as follows: When. the commutator is in the positionshown in Fig. 1, alternating current flows from the source S in thedirection indicated by the arrows in F 1 through the inductance L tobrush b segment 7 brush 6,,the inductance L, the resistance R, brushes 5and b segment 2 and thence back to the source by way of the brushes?)and Z), and the cross-conductor ;1 As will be obvious, the arrangementof brushes and commutator segments is such that the connections of thesource to the working currentare short-circuited twice during everycycle and current is supplied to the working circuit from. the sourcetwice every cycle, andalso that the duration or" the time that saidconnections are short-circuitcd is substantially equal to the timeduring which current supplied from the source to the working circuit. ii hen the commutator is in such position that said connections aresl1ort-.:ircui ted, for example, wh n it has the position shown in Fig.2, current will flow from the source 8 through the inductance L to thebrush 7),, segment r brush 5,, thence by way of thc 'cross conductor a:to brush 7),, segment a" and thence back to the source by way elf-thebrushes a, 6 The M. of self induction in the workingcircuit due to theenergy stored in the inductance L will cause a current to fiow in thedirection indicated by the arrow over said coil, as follows: through theresistance R to conductor 00, brush 6,, segment 1 and thence back to theinductance L by way of brush 7),. Current in the supply circuit willhave the following path: from source S, in-

ductance L, brush b segment 1",, brush 6,, conductor :11, brush 6,,segment 7 and thence back to the source by way of the brushes 7), b andthe cross-conductor 3 During this period of short-circuit thealternating E. M. F. of the source reverses the direction of currentflow in the inductance L, said current being equal in value to thecurrent in the working circuit at the instant of removal of theshort-circuit. Under these conditions, sparkless commutation willresult, and these conditions may be produced by adjustment of the rockerarm. It will be readily understood that if the source S is asubstantially constant-potential alternating current source, directcurrent will be developed in the working circuit on a substantiallyconstant-current basis.

It will be understood that various modifications may be made, both inthe apparatus and circuit connections herein shown and described,without departing from the principle of my invention.

I claim:----

1. A system for converting constant-potential A. C. to substantiallyconstantcurrent D. C. comprising, in combination, a source ofconstant-potential A. C.-, a working circuit, an inductance in serieswith the source of A. C. for controlling the value of current in saidworking circuit, a synchronously driven commutator for controlling theconnection of said source to said working circuit, and an inductance inseries with said working circuit of value large compared to that of thefirst-mentioned inductance.

2. A system for converting constant-potential A. C. to substantiallyconstant-current D. 0. comprising, in combination, a source ofconstantpotential A. (1., a Working circuit, an inductance in serieswith said source of A. C. for controlling, the value of current in saidworking circuit, a synchro nously driven commutator, brushes connectingsaid. commutator with said source and I with said working circuit, saidbrushes be ing spaced around said commutator to connect said source tosaid working circuit twice during every cycle, means for shortcircuitingthe connections of said source to said working circuit tw e during everyin series to said large compared ad I sc ance.

-ins-tant-pocycle, and an inductance working circuit of r" with thefirstmcntio 3. A system for can nuance tential A. C. to substantiallyconstant-current D. C. source of constant-potential A. (1., a workingcircuit, an inductance in series with the source of A. C., asynchronously-driven commutator for controlling the connection of saidsource to said working circuit, and an inductance in s ries with saidworking circuit, the value of the first mentioned inductance in henriesbeing approximately equal to the maximum E. M. F. of said source dividedby twelve times the product of the amperes in the working circuit by thefrequency of the current of the source in cycles per second.

4x. A system for converting constant-potcntial A. C. to substantiallyconstant-current I). C. comprising, in combination, a source ofconstantqiotential A. (1, a working circuit, an inductance in serieswith the source of A. O, a synchronously driven commutator forcontrolling the connection of said source to said working circuit, andan inductance in series witl'rsaid working circuit, the value of thefirst mentioned inductance in hcnries being approximately equal to themaximum E. M. F. of said source divided by twelve times the prdduct ofthe amperes in the working circuit by 'the frequency oi the current ofthe source in cycles com risin in combination a per second and the valueof the last mensource of A. C. for controllin the value of 3 current insaid working circuit, a. synchronously driven commutator, brushesconnecting said commutator with said source and witl said workingcircuit, said brushes being spaced around said commutator to con nectsaid source to said working circuit twice during ry cycle, means forshort" circuiting mentions of said. source to said working circuit twiceduring every cycle, the durati n of such short-circuit beingapproximately equal to the duration of a quarter of a cycle oi thealternating current developed by the source, and an inductance in serieswith said working circuit of value large compared to the first mentionedinductance.

in testimony whereof, I have hereunto subscribed my name this 1.6 day ofAug. liilii.

SEiVALL CABOT.

Witnesses PAT-nick J. Connor, 1 3120. hi. .i oonwoarn.

